Muscle-powered cardiac assist systems been developed to aid patients with chronically and unacceptably low cardiac output, and who cannot have their cardiac output raised to acceptable levels by traditional treatments such as drug therapy. (See G. L. Anstadt & W. E. Britz, Jr., Continued Studies in Prolonged Circulatory Support by Direct Mechanical Ventricular Assistance, 14 Trans. Amer. Soc. Artif. Int. Organs 297 (1968)). U.S. Pat. No. 4,813,952 issued to Khalafalla, which is hereby incorporated by reference, teaches a cardiac assist system powered by surgically modified muscle tissue, such as the latissimus dorsi flap, using cardiomyoplasty techniques. Being fast twitch muscle tissue, the latissimus dorsi can be converted to slow twitch tissue for efficient long-term use by using the techniques taught in U.S. Pat. No. 4,411,268 issued to Cox, and also hereby incorporated by reference.
In a system using muscle wrapped about an ailing heart, an implantable pulse generator (IPG) senses contractions of a heart via one or more sensing leads, and stimulates the appropriate nerves of the muscle tissue (via stimulation leads) to cause the muscle tissue to contract in synchrony with the heart chamber of interest. As a result, the heart is made to contract more forcefully, raising the stroke volume, and hence cardiac output.
IPGs typically include end-of-life (EOL) indication circuitry for detecting and indicating an approaching depleted battery state. In prior art cardiac pacemakers, a typical response to an EOL condition is to lower the pacing rate.
A special EOL indication signal can be transmitted transtelephonically from the IPG (whether cardiac, neuromuscular, etc.) when the patient is at a remote location. However, this requires specific special equipment at the receiver end to properly interpret the signal as an EOL signal. Thus, without the special equipment, a clinician interpreting the transtelephonic data would not know that an EOL condition is imminent, and would not then be able to advise the patient that the time for replacement of the IPG has arrived.